This invention relates to a method and system of noise attenuation around an air induction assembly.
Manufacturers have employed active and passive methods to reduce engine noise within the passenger compartment. Such noise frequently emanates from the engine, travels through the air induction system and emanates out of the mouth of the air intake into the passenger compartment. Efforts have been made to reduce the amount of engine noise traveling through the air induction system. These efforts include the use of both passive devices such as expansion chambers and Helmholtz resonators and active devices involving anti-noise generators.
Active systems use a speaker to create a canceling sound that attenuates engine noise. The sound created is out of phase with the engine noise and combines with this noise to result in its reduction. Generally, this sound is generated in proximity to the mouth of the air induction system. In one such system, a control unit, such as a digital signal processor, obtains data from the vehicle engine, creates a predictive model of engine noise, and thereby generates the appropriate cancellation signal based on the results of this model. This signal is then transmitted to the speaker, which transforms this signal into a canceling sound. Because the control unit may not perfectly model engine noise, an error microphone is placed in proximity to the mouth of the air induction system to determine if engine noise need be further attenuated.
Current active noise systems are positioned in the engine compartment of vehicles. The location is hostile, however, to the electric components of these systems. Heat and noise from the engine as well as exposure to environmental road conditions may all affect the durability and performance of such systems. Indeed, even sprayers from car washes may harm components such as speaker and microphone.
A need therefore exists for a more environmentally robust system.
The present invention protects critical components of the air induction system from the harsh environment of the engine compartment of a vehicle as well as ambient conditions that may exist outside of the vehicle. This objective is accomplished by placing these components in the fender cavity of the vehicle rather than under the hood and within the engine compartment. The inner fender protects the air induction system from the hostile temperatures and conditions around the vehicle engine while the outer fender protects the system from the environment outside of the vehicle.
The invention has at least an air induction body with a mouth and a speaker forming an interface for noise attenuation with the mouth. As known, a control unit determines the speaker output and attenuates noise by generating a sound out of phase with the noise. One embodiment of the invention involves the placement of the interface within the protected confines of a vehicle fender cavity. Portions of the fender thereby protect components such as the speaker and microphone from the elements.
To fit the system within the fender cavity, the speaker may be placed outside of the air induction body rather than in the body as with many other systems. This configuration thereby takes up less space than these other systems. A microphone disposed about the interface serves to provide feedback to the control unit as to whether further attenuation is required. The microphone may be at least partially covered and protected by a portion of the fender. The microphone may be mounted with the speaker as well. Mounting the speaker and microphone together in the fender cavity not only protects both of these components but also enhance noise attenuation by inhibiting the speaker from vibrating relative to the microphone.
A wave guide serves to direct the noise attenuating sound from the speaker to the interface. The wave guide may further serve to cover and protect the speaker in addition to directing the noise attenuating sound. A speaker chamber forms an acoustic mass with the speaker, permitting the speaker to generate low frequency sounds for improved noise attenuation. The speaker chamber may include a venting port.
Another embodiment of the invention involves the formation of a dipole inlet at the interface of noise attenuation. This dipole inlet along with the interface are located within the fender cavity for protection. Additionally, the dipole inlet serves to improve noise attenuation by limiting the amount of sound emanating from the speaker mouth. Again, the speaker may be located outside of the air induction body and may employ a wave guide to direct noise attenuating sound from the speaker to the interface. Wave guide may cover and protect the speaker. A speaker chamber with and without vented port may be employed as well.